There are really two tiers of cyclocross bikes. There are the top tier CX bikes, and there everything Russell wrote is spot on, in spades. Then there are the lower end CX bikes, like my Bianchi Axis, which are really hybrids, designed and marketed as a spirited all weather commuter, weekend fun (road and/or dirt), light touring, and perhaps some real cyclocross racing in the lower divisions. I read that CX sales have been growing at something like 40% for the last couple of years. CX racing has not.
Bouncing off Russells and others comments on cyclocross bikes for touring: My one and only bicycle is my Bianchi cyclocross. I went in the bike shop intending to buy the steel Bianchi Volpe, which does have cross like geometry, and I was given the aluminum Axis to compare and bought the Axis on the spot. The liveliness was a noticeable difference.
The rear dropouts are drilled and threaded for fenders and/or racks, and the seat stays have eyelets. Many other CX bikes have similar setups; Surly and Soma are two (Soma only sells frames). I got a Tubus Logo rear rack, which fit perfectly. The Logo puts the panniers down and back, and my size 11 shoes have room to spare. CX frames have the bottom bracket up a little higher and a shorter wheelbase than most touring frames, which is balance/handling consideration, especially for fully loaded setups. At best it is a light to medium weight rig.
The fork is carbon/aluminum (and are on many CX bikes), and is set up for fenders only. I think the Surly has an optional steel fork with low rider mounts. I put on a small brake-boss mounted rack designed for mountain bikes. I got it from Nashbar, and it is rated at 15 lbs. I strap a little soft-sided six-pack cooler to it with maybe 7 to 9 lbs max.
The wheels: 16 front and 20 holes rear hubs, flat blade spokes, with deep aluminum rims. The little bit of dirt riding I did and pulling an overloaded trailer down the Oregon coast last summer the wheels did fine. On my last trip of the year with my new rack and panniers a spoke and the rear axle broke on some course pavement (those fiber spokes work!). Our dearly departed brother Sheldon Brown has testified to Bianchi cutting corners on the wheels and pedals, and he sold them. I now have 32/36 Shimano hubs and Mavic touring rims.
Im some what a follower of Lao Tzu when he says, A wise traveler has no fixed plans and is not intent upon arriving, and Robert Frost, Two roads diverged in a wood, and I I took the one less traveled by, and that has made all the difference. This is where the CX comes into its own for touring. I carry my dirt tires as my spares. A CX frame allows you to get pretty fat and knobby between the forks and stays. And that opens up lots of one less traveled by. To be fair there are some touring frames that can take fairly wide tires.
If I were younger and planning a trip around the world with ADVENTURE in my eyes, I would be looking pretty hard at the Surly Travelers Check. Im looking anyhow.
Western Flyer
My hip hurts when I move my chin, . . .
and my heart is--what?
What's that? What's that you say?
You say today is. . .Saturday?
G'bye, I'm going out to play!
Shel Silverstein